NAME¶
rtf_create_chebychev, rtf_create_butterworth - Creates IIR Chebychev and
Butterwoth filters
SYNOPSIS¶
#include <rtf_common.h>
hfilter rtf_create_chebychev(unsigned int nchann, int
proctype,
double fc, unsigned int num_pole,
int highpass, double r);
hfilter rtf_create_butterworth(unsigned int nchann, int
proctype,
double fc, unsigned int num_pole,
int highpass);
DESCRIPTION¶
rtf_create_chebychev() creates a IIR chebychev filter processing
nchann channels of data type specified by
proctype with
fc as normalized cutoff frequency, whose the Z-transform has
num_pole poles and whose the impulse response has a ripple of
r
This latter is expressed as the ratio between the overshoot (difference
between the max value of the response to a unit step and the unit length) and
the unit length (ratio
not expressed in decibels).
rtf_create_butterworth() is the same as
rtf_create_chebychev() but
creates a butterworth filter (which a special case of a chebychev filter with
a ripple of 0).
A normalized frequency is the ratio between the absolute frequency and the
sampling frequency (i.e. a value of 1.0 refers to the sampling frequency).
If
highpass is 0, it specifies the filter should be a lowpass. If
highpass is non-zero, the should be a highpass.
RETURN VALUE¶
Returns the handle to the created filter in case of success, NULL otherwise.
SEE ALSO¶
rtf_create_filter(3),
rtf_destroy_filter(3)